Mass spectrometer

Abstract

Herein disclosed is an atmospheric pressure ionization mass spectrometer having a mediate pressure region, wherein a jet separator is incorporated for playing a double role of differential pumping and concentration of the electric field, and wherein a gas jetting aperture of the jet separator and another aperture for introducing a gas to an analyzing region of the spectrometer are made of a conductive body and are adapted to be kept at different electric potentials.

What is claimed is: 
     
       1. An atmospheric pressure ionization mass spectrometer comprising an ionization region maintained at about atmospheric pressure for ionizing a sample, a mediate pressure region maintained at about 0.1 to 10 Torr and a highly evacuated mass spectral region provided at its upstream side with auxiliary ionization means, a first partition wall separating said ionization region and said mediate pressure region for each other, at least a part of said partition wall being made of a conductive material to form a first electrode, a first fine aperture formed in said first electrode for effecting communication of said ionization region and said mediate pressure region with each other, a second partition wall separating said mediate pressure region and said mass spectral region from each other, at least a part of said second partition wall being formed of a conductive material to form a second electrode, a second fine aperture formed in said second electrode for effecting communication of said mediate pressure region and said mass spectral region with each other, said fine apertures in combination forming a jet separator, and means for applying an electric potential between said first and second electrodes. 
     
     
       2. A mass spectrometer as claimed in claim 1, wherein the distance between said first and second fine apertures is about 0.5 to 20 mm. 
     
     
       3. A mass spectrometer as claimed in claim 2, wherein said distance is about 0.5 to 2 mm. 
     
     
       4. A mass spectrometer as claimed in claim 2, wherein said distance is about 2 to 20 mm. 
     
     
       5. A mass spectrometer as claimed in claim 4, wherein said distance is about 4 to 10 mm. 
     
     
       6. A mass spectrometer as claimed in claim 1, wherein said auxiliary ionization means is of the electron impact type. 
     
     
       7. A mass spectrometer as claimed in claim 1, wherein said ionization region is kept almost at atmospheric pressure. 
     
     
       8. A mass spectrometer as claimed in claim 1, wherein said mediate pressure region is kept at about 0.1 to 10 Torr. 
     
     
       9. A mass spectrometer as claimed in claim 1, wherein said ionization means in said ionization region is of the corona discharge type. 
     
     
       10. A mass spectrometer as claimed in claim 1, wherein said ionization means in said ionization region is of the radioisotope type. 
     
     
       11. A mass spectrometer as defined in claim 1, wherein said first and second fine apertures are 60 micrometers and 200 micrometers, respectively.